Influences of La on Optical and Electric Properties of BiFeO3 Thin Films

Bismuth ferrite (BiFeO3, short for BFO) is an important roomtemperature single phase multiferroic materials. To further improve electric properties of BFO, La3+ was introduced. Bi1-xLaxFeO3 (x = 0-0.12) thin films were fabricated by sol-gel method. The microstructure, optical and electric properties of Bi1-xLaxFeO3 thin films have been investigated. XRD results show that Bi1-xLaxFeO3 thin films is rhombohedral distortion perovskite structure and the addition of La3+ can inhibit the formation of impure phase. The substitution of La3+ for Bi3+ on A sites can restrain the growth of grain and improve the roughness of thin films. The band gap of Bi1-xLaxFeO3 thin films is less than that of BFO thin films, and its band gap decreases first and then increases as the content of La3+ increases, which results from both Burstein-Moss effect and impurity level. A larger amount of La3+ (x = 0.12) can make leakage current of BFO thin films obviously decrease. Moreover, the remnant polarization and coercive electric field of Bi1-xLaxFeO3 thin films increase with the increasing of La3+ content. It results from the decrease of oxygen vacancy and effects of grain size.